Power semiconductor devices among semiconductor devices are being used to control or rectify comparatively high electric power in vehicles such as railroad cars, hybrid vehicles and electric vehicles, home appliances, industrial machines, etc. Since the power semiconductor element develops heat during use, there is a need for the power semiconductor device to have the ability to dissipate heat from the element. Also, because a high voltage of several hundred volts or higher is applied, insulation from the outside of the device is required.
An intelligent power module (IPM) is a module in which a power semiconductor element and a control semiconductor element are combined integrally with each other. If a lead frame is used as wiring material, the power semiconductor element and the control semiconductor element are ordinarily mounted on a die pad physically isolated and are thereafter electrically connected to each other by thin metal wires or the like. Since a large current is caused to flow through the power semiconductor element, a large amount of heat is generated and there is a demand for imparting a heat dissipation capacity to the module.
As a heat dissipating structure, a structure is known in which a metal plate is heat-pressure-bonded to back surfaces of a die pad with high-heat-dissipation insulating film interposed therebetween and these members are molded by transfer molding (see, for example, PTL 1).